Week 4 - Cardiovascular 2 Flashcards
(32 cards)
Cardiac output
- amount of blood pumped out by each ventricle in 1 min
- calculation: HEART RATE & STROKE VOL
- affected by autonomic activity, hormones & temp
- CARDIAC RESERVE: diff vetween max & resting CO, inc. w/ fitness, dec. with disease
Heartrate - regulation factors
- Pacemaker cells
- Neural control from ANS
→ Sympathetic inc. HR
→ Parasympathetic dec. HR - hormones
- conc. of ions in blood (Na+, K+, Ca2+)
- age
- gender
- physical fitness levels
- temp
Cardiac output - stroke volume
STROKE VOL = END DIASTOLIC VOL - END SYSTOLIC VOL
EDV: max blood collected in ventricles at end of diastole
influenced by: Filling time
- VENOUS RETURN: amount of venous blood returned to heart
- PRELOAD: pressure on cardiac wall due to blood vol
ESV: blood in ventricle at end of systole
influenced by: CONTRACTILITY: symp. stimulation inc. contractility, drugs reduce this
- AFTERLOAD : force ventricles produced to open valves, reject blood
preload
Length or degree of stretch of sarcomeres in ventricular cells before contract
FRANK STARLING LAW: inc ventricular muscles stretch, leads to more forceful contraction
afterload
Force that right & left ventricles must OVERCOME in order to EJECT blood into their respective arteries
contractility
hearts intrinsic pump ability to GENERATE TENSION
cardiac contractility - regulation
- HORMONAL CONTROL
- hormones (thyroid or norepinephrine) can beta-adrenergic receptors in cardiac cells, opening Ca2+ CHANNELS
- opening of Ca2+ channels inc. length of plateau phase of ventricular depolarisation, prolonging ventricular contraction
SNS: sympathetic nerve fibres release norepinephrine
cardiac output- effect of exercise
- PROPRIOCEPTORS: HR inc. at beginning bc. signals from joints & muscles
- VENOUS RETURN: muscular activity inc. venous return causes inc SV
- inc HR & inc SV cause inc. CO
- sustained exercise programs produce VENTRICULAR HYPERTROPHY
- inc SV allows heart to beat more slowly at rest
inc. cardiac reserve
veins
LARGE: inc superior & inferior vena cava contain 3 vessel wall layers; slender tunica media: ELASTIC & COLLAGEN FIBRES
MEDIUM: 2-9mm (diametre) - thin tunica media - SMOOTH MUSCLE CELLS & COLLAGEN FIBRES. tunica externa - THICKEST: SMOOTH MUSCLE CELLS & LONGITUDINAL BUNDLES OF ELASTIC COLLAGEN FIBRES
VENULES: collect blood from capillary beds- smaller than 50 micrometres → lack tunica media
arteries
ELASTIC: inc. pulmonary trunk & aorta - resilient, capable of STRETCHING & RECOILING as heart beats & arterial pressure changes
MUSCULAR: distribute blood to body’s skeletal muscles & internal organs
ARTERIOLES: poorly defined tunica externa, one or two layers of smooth muscle cells
capillaries
- SMALLEST BLOOD VESSEL
- deliver blood to TISSUES & CELLS
- lumen big enough for a single erythrocyte to pass
- most tissues have a rich capillary supply )except tendons, ligaments & cartilage)
- Function: EXCHANGE 02, CO2 NUTRIENTS, HORMONES BETWEEN BLOOD & INTERSTITIAL FLUID
Capillaries (types) - Continuous
- occur in most tissues
- endothelial cells have tight junctions w/ intercellular clefts (allow water & small solutes)
Capillaries (types) - Fenestrated
- kidneys, small intestines, hypothalamus
- organs that require rapid absorption or filtration
- filtration pores; allow passage of molecules
Capillaries (types) - Sinusoids
- liver, bone marrow, spleen, endocrine organs
- irregular blood-filled spaces; some have large fenestrations
- allow proteins & blood cells to enter
venous system
- low pressure (~10% press. in ascending aorta)
- contain valves to prevent back flow of blood →defects cause varicose veins/hemorrhoids
- 64% of total blood volume in venous system
venous return
- gravity helps drain blood form head & neck of skeletal & thoracic pumps help w/ venous return from lower body
- SKELETAL MUSCLE PUMP: in the limbs contraction of muslce exerts pressure on veins & valves direct blood towards the heart; no back flow
- THORACIC RESPIRATORY PUMP: works through dec. thoracic pressure during inhalation draws blood into thoracic veins & right atrium
- improved by exercise
capillaries - exchange
- water, small molecules, ions: cross capillary walls adjacent endothelial cells or fenestrated pores
- other ions (Na+, K+, Ca2+): cross walls through chanells
- large water soluble compounds: cannot cross wall except in fenestrated capillaries
- lipids, respiratory gases: can diffuse through endothelial cells
- plasma protein: cannot cross walls except at sinusoids of liver
Capillary exchange - filtration
- selective movement of material in instertitial fluid through capillary walls → act as a filter, directed OUTWARDS
- promoted by BLOOD HYDROSTATIC PRESSURE
Capillary exchange - reabsorption
- movement of material from instertitial fluid into capillaries - directed INWARDS
- promoted by BLOOD COLLOID OSMOTIC PRESSURE
Circulation - blood flow
- measure in ml/min. amount of blood flow through an area in given time, blood flow through entire vascular sys = cardiac output & fairy constant while blood flow through specific organs vary
Circulation - blood pressure
- measured in MMHG → force per unit area the blood exerts on a vessel wall
- refers to systemic arterial BP in largest arteries near heart
- diff in BP (BP Gradient) is driving force that keeps blood moving
peripheral resistance
refers to opposition to blood flow & is measure of friction encountered by blood on its passage through vessels
- VISCOSITY: thickness of fluid due to formed elements in blood, constant unless disease
- VESSEL LENGTH: inc. length increases resistance → constant
- VESSEL DIAMETRE: smaller diametre = inc resistance varies inversely W/ THE FOURTH POWER OF VESSEL RADIUS. turbulences inc resistance
blood pressure - arterial
- force that blood exerts against a vessel wall measured at brachial artery of arm
- SYSTOLIC PRESS: BP during ventricuar systole
- DIASTOLIC PRESS: BP during ventricular diastole
- NORMAL - young adult: 120/80 mmHg
PULSE PRESSURE: systolic -diastolic → stress exerted on small arteries
MEANARTERIAL PRESSURE: measurements taken at intervals of cardiac cycle. diastolic presss + (1/3 pulse press)
blood pressure - systemic
- pumping of heart generates blood flow
- pressure arises from resistance
- systemic BP is highest in aorta & declines until it reaches O at the right atrium
- most pronounced change in BP occurs in arterioles
